The invention concerns a technique to transmit data from a sender to a receiver via a network, preferably via networks such as a LAN and/or the Internet etc., where the sender transmits data to a base station and where the sender is verified via a server, in particular via servers such as a AAA (Authentication, Authorization, Accounting) server. Such a AAA server is located in the network and is typically used to authenticate a device or user and then to authorize the device or user to access services under defined conditions, following which accounting may be supported.
During the transmission of data, security mechanisms are especially important to protect a legitimate sender from an illegitimate sender. If there are no such protections, an illegitimate sender may pretend to be a legitimate sender, i.e. the illegitimate sender operates using the ID of the legitimate sender, sends data and thus transmits data free of charge to any receiver. The sender could e.g. be a computer that supports data transmission.
In general, a server, often equipped as a AAA server, verifies the sender. The AAA server serves to authenticate the legitimate sender, i.e. to ensure that the sender registers himself and proves that he is the authorized person. The authentication can be done e.g. via a login and/or by entering a password. The AAA server subsequently authorizes that sender to use services to a defined extent, and under well-established conditions.
Once a sender has been authenticated successfully, an illegitimate sender may acquire the identity of the legitimate sender and use the existing connection or even take on the role of the legitimate sender after the connection has been terminated. The illegitimate sender can thus transmit data to any destination free of charge. This is to the disadvantage of the legitimate sender if charging is based on the transmitted data volume and to the disadvantage of the provider in case flat rate charging has been agreed to between the legitimate sender and the provider for data transmission.